AIB has promised that thousands of shoppers who were double-charged when they used debit and credit cards will not end up having to pay bank charges or overdraft fees because of the blunder..

People who bought goods and services with plastic cards on Monday ended up being charged twice when they used terminals supplied to retailers by a firm part-owned by AIB.

The blunder involved some 48,000 card users who made a combined total of 88,000 transactions, valued at €5m.

And anyone who had a refund processed on the same day ended up getting double the amount of money they were due. A problem with 15,000 pointof-sale terminals supplied by AIB Card Services led to the double-charging.

If a customer paid €20 using one of the machines, €40 was deducted from their card.

Any purchases made with either Visa or MasterCard debit, credit and pre-paid cards were double-charged. The blunder affected cards issued by any bank, and not just AIB. However, Laser card transactions escaped the mess-up.

Una Dillon of the Irish Payments Services Organisation, a representative body for the payments industry, advised consumers to check their bank accounts to see if they have been overcharged, and if they have, to ensure the refunds have gone through.

A technical fault meant that terminals supplied by AIB Merchant Services (AIBMS) double-charged customers and also credited retailers on the double, in error.

AIB Merchant Services (AIBMS) said all affected customers would now be refundedThe company is a joint venture between international electronic commerce and payment services firm First Data Corporation and AIB. First Data processes AIBMS transactions.

The technical fault occurred at First Data's processing operation in Germany. The fault has been resolved, the card services firm said.

AIBMS said it was working to ensure that affected customers are reimbursed promptly and apologised for any inconvenience caused.

Refunds are expected to appear in customer accounts in days.

"The money will go back into customers' accounts automatically but if they want to double-check, they can contact their branch," an AIBMS spokeswoman said.

The double-charging could mean that some consumers could end up being overdrawn on their current accounts.

Others could incur fees and charges if the balance in their account has dipped below certain levels.

With Bank of Ireland, customers are charged transaction fees if they fail to keep at least €3,000 in their accounts. AIB charges fees if balances dip below €2,500 at any stage in a three-month period.

Yesterday, AIB Card Services insisted it would make sure there were no charges imposed on account holders in any bank due to its double-charging blunder.

Customers worried that they have been overcharged can contact the company on the following number: 0818724724, or at their local AIB branch.

Cardholders should contact their issuing bank, which will confirm the credit has been posted to their account, the company said.